This invention is directed to a method for the regeneration of catalysts which are useful in processes wherein various oleaginous base stocks are upgraded, for example, catalysts which are used in lube or distillate dewaxing processes.
It is well known in the art to regenerate catalyst systems by flushing them with steam or water, or a suitable hot gas or vapor, or even subjecting the catalyst to combustion to remove the impurities or poisons such as nitrogen compounds and various other carbonaceous matter which the catalysts have acquired during their utilization.
Spent or end-of-cycle catalysts, e.g., lube dewaxing or distillate dewaxing catalysts, such as for example, zeolites and the binders thereof, contain acquired nitrogen compounds which poision the catalyst and thereby render it less effective with respect to activity. The nature of these nitrogen poisons is not precisely known, but they are thought to be aromatic in character and are of the basic type. Typical basicities for aromatic amines are in the order of K.sub.b =10.sup.-10 (Ref.: Organic Chemistry, 2nd Ed., Morrison and Boyd, page 721). These basic nitrogen compounds are generally classified (Re.: The Chemistry and Technology of Petroleum, James G. Speight, pg, 72-5, 1980) as being homologues of pyridine and pyrrole. Their K.sub.b 's are about 2.times.10.sup.-9 and 1.times.10.sup.-14, respectively.
One well known regeneration procedure for these types of catalysts is to pass hydrogen over the catalyst at about 400 psig at a temperature of 900.degree.-1000.degree. F. for about 24 hours. However, despite this treatment, residual nitrogen remains on the catalyst. To alleviate this problem of not being able to remove substantially all the nitrogen poisons, the novel procedure disclosed hereinbelow is offered.